1. Field of the Invention
The present invention relates to a wiring substrate and a display device including the same.
2. Description of the Related Art
In recent years, a flip chip mounting method using an anisotropic electrically conductive film (hereinafter, sometimes referred to as “ACF”) or an anisotropic electrically conductive paste (hereinafter, sometimes referred to as “ACP”) or the like has been widely used as a method for mounting an integrated circuit chip (hereinafter, sometimes referred to as an “IC chip”) to a wiring substrate. See, for example, Japanese Laid-Open Patent Publication No. 9-244047.
However, in the case where an IC chip is flip chip mounted with an ACF or ACP, adjacent terminals and bump electrodes are short-circuited by electrically conductive fine particles included in the ACF and the like, causing a leakage current. Adjacent terminals and bump electrodes are likely to be short-circuited especially in the case where a fine-pitch IC chip having closely spaced bump electrodes is mounted. Adjacent terminals and bump electrodes are also likely to be short-circuited in the case where the concentration of electrically conductive fine particles is increased to assure electric connection between terminals and bump electrodes.
Japanese Laid-Open Patent Publication No. 9-244047 discloses a liquid crystal display device having a passivation film (wall) between wirings on a substrate (see FIG. 1 of Japanese Laid-Open Patent Publication No. 9-244047). This passivation film is not provided in order to suppress generation of leakage current, but to prevent electrically conductive particles from going out from the space between a bump electrode and a terminal in a heat pressure bonding process of an anisotropic electrically conductive film. In the liquid crystal display device of Japanese Laid-Open Patent Publication No. 9-244047, wirings on the substrate are isolated from each other by the passivation film. Therefore, outflow of electrically conductive particles can be suppressed and short-circuiting between wirings can also be suppressed to some extent. However, the space between adjacent bump electrodes is filled with an anisotropic electrically conductive film and adjacent bump electrodes are not isolated from each other by the passivation film. Therefore, in the liquid crystal display device of Japanese Laid-Open Patent Publication No. 9-244047, adjacent bump electrodes may be short-circuited by electrically conductive fine particles and generation of leakage current is not sufficiently suppressed.